The invention relates to a device pursuant to the preamble of Claim 1 as well as pursuant to the preamble of Claim 12.
Such devices intended for irradiating media with UV light are generally known. In this connection, the wish is that the devices for irradiating media with UV light be more effective in their treatment effect than possible chemical methods, with the same economic efficiency. This presupposes a high UV light/space/time yield with the lowest possible energy and apparatus expenditure.
For implementation of these devices, a combination between the irradiation space and the UV light source arrangement is generally striven for, in which each volume element of the medium is irradiated with the same UV dose, to the greatest extent possible. The ideal case to achieve the highest degree of effectiveness consists of having the average dose be equal to the minimum dose. To achieve this goal, the following criteria must be optimized:
1. avoiding radiation losses; PA1 2. achieving the most uniform irradiation intensity possible; PA1 3. achieving the most uniform contact time and/or flow velocity possible.
The prerequisites pursuant to Numbers 2 and 3 can often only be fulfilled by means of complicated auxiliary equipment for swirling up the medium to be sterilized or treated.
The invention is based on the task of improving a device for irradiating flowing liquids and/or gases with UV light, so that radiation losses are reduced, in order to achieve the most uniform irradiation intensity possible, and furthermore so that uniform contact times can be achieved, all with a simple structure.
Pursuant to a first alternative, this task is accomplished with the characterizing features of Claim 1, for the device stated in the preamble of Claim 1.
The new device is designed for installation in a pipeline, and has a new type of radiation distribution for this purpose, with which the criteria mentioned above can be fulfilled to a great extent. The use of a pipeline means that a pressure system is involved, in which the medium (liquid and/or gases) is passed through the pipeline by means of pressure.
Optionally, either a single or several quartz protective pipes, each equipped with a rod-shaped UV light source, are arranged in the center of the housing and perpendicular to the flow direction of the medium. Whether one or several UV light sources are used depends on the desired throughput amount. For high throughput performance, a greater number of UV light sources is used, arranged next to one another and in a maximum of two rows. If arranged in two rows, the UV light sources are offset relative to one another in the flow direction of the medium.
The UV light sources preferably have a flat oval cross-section and special radiation characteristics, as well as higher electrical outputs, in comparison with known UV light sources with a round cross-section. For a flat emitter--in other words for a UV light source with a flat oval cross-section--the radiation flow is emitted 3/4 via the broad side and only 1/4 via the narrow side. Radiation via the broad side also is much more bundled than for UV light sources with a round cross-section. The UV light sources emit greater than 50% of their emitted light via the broad side flat walls, and lesser than 50% via the narrow side oval walls.
This results in UV emission with the maximum directed towards the two flat sides. By arranging one or several UV light sources (flat emitters) in a plane perpendicular to the flow direction and adjacent to the connection openings of the housing or the connected pipeline, the maximum of the UV emission reaches the connected pipeline with the radiation going essentially parallel, specifically reaching both the inflowing and the outflowing medium in equal parts.
Since the upstream and downstream pipeline is supposed to run in a straight line with the radiation direction, the radiation can penetrate into the medium without loss, i.e. until it is completely absorbed. This has not been the case with the devices known until now.
Although a device for sterilization of liquids is known from Austrian Patent 362 076, in which a radiation loss is prevented to a great extent by using reflectors, a large part of the radiation is still lost after it passes through the irradiation chamber.
Such disadvantages of the known devices are eliminated with the device according to the invention (which is also designated as a UV light barrier). Due to its construction and the directed distribution of radiation, wall losses are equalized to a great extent. With a high density of rays, an almost homogeneous distribution of radiation in the medium to be treated, as well as transfer of the radiation flow with little loss, i.e. almost complete absorption of the UV emission in the medium, is guaranteed.
Due to the directed and essentially parallel alignment of the UV emission, the mathematical limit case of an expansive level source of rays is approached, and the weakening of irradiation intensity with an increasing distance from the source of the rays, caused due to geometry, is avoided to a great extent.
Since the flow direction and the radiation direction are parallel, it follows that the dose applied to one volume element of the medium results from the quotient of the irradiation intensity and the flow velocity of the medium, integrated over the entire length of the pipeline.
The dependence of the dose applied on the distance to the axis must be taken into consideration by multiplication with the ratio of the radial distribution of the irradiation intensity and velocity. Spacial differences in the irradiation intensity in the axial direction are therefore equalized by taking the average across the path of the volume element. With this taking of the average, the dependence of the irradiation intensity on the axial distance to the source of the rays is eliminated. A high degree of uniform distribution of the dose applied to each volume element is the result.
The radial distribution of the irradiation intensity possesses a flat maximum in the center of the pipe, and weakens as it approaches the edge of the pipe. The radial distribution of the velocity has a similar profile. Model calculations show that the quotient of both distribution functions is constant within .+-.10% over the entire pipe cross-section, depending on the flow velocity and the emitter arrangement.
In a device according to the invention, in contrast to conventional UV irradiation systems, for the first time the same UV dose is applied to each volume element, within a variation range of a few percentage points.
Computer simulations have shown the exemplary performance capacity of a device according to the invention, as shown in the table below, taking into consideration marginal effects, changes in cross-section, UV transmission of water as well as the arrangement of the UV light sources. The table shows a calculated comparison of the performance capacity of a known device, with a according to the invention (at a dose of 35 mWs/cm.sup.2).
______________________________________ Device Prior Art Invention Number of UV emitters 4 5 effective UV output (254 nm) 184 W 158 W throughput: T (1 cm) = 96% 80 m.sup.3 /h 106 m.sup.3 /h T (1 cm) = 90% 59 m.sup.3 /h 74 m.sup.3 /h ______________________________________
Device according to the invention: diameter of the pipeline 250 mm; net cross-section 511 cm.sup.2. Reactor volume for the known device: 31 liters.
A device according to the invention is characterized by a degree of effectiveness that is approximately 50% higher than that of a conventional device with the emitter arrangement in the flow direction.
The directed radiation of the UV emission, the arrangement of the UV light sources relative to one another and perpendicular to the flow direction, as well as the adapted housing shape of the device, result in a degree of effectiveness previously not achieved in the transfer of UV light radiation to the medium to be treated, which cannot be achieved with devices known until now.
A special advantage of the invention is that the new device is suited for being subsequently installed in an existing pipeline, with the device simply being inserted as an intermediate piece.
Pursuant to another alternative, the task on which the invention is based is accomplished with the features indicated in the characterizing section of Claim 12, for a device according to the preamble of Claim 12.
Here, there is no pipeline, and instead, a flume through which liquid flows, such as those used in sewage treatment plants, is used.
In other words, this is a pressure-free system, with the flume being understood as a housing open towards the top.
This form of a solution also results in the advantages for sterilization of liquids by means of UV radiation that is directed and extends in a straight line in the direction of the flume, which is also in a straight line, as described above,
Preferably, several UV light sources brought together in one or even several rows can be structured as a kind of emitter module, which is easy to handle and therefore can also be simply inserted into the flume from above. If needed, several such emitter modules can be placed into the flume at certain intervals from one another.
In the following, the invention is explained in more detail on the basis of the embodiments shown in the drawing. This shows: